Electrodepositing composition and bath



Patented Dec. 28, 1948 4 ELECTRODEPOSITING COMPOSITION AND BATH Raymond A. Hoflman, Euclid, Ohio, assignor to E. I. du Pont de Nemours & .Company, Wilmington, Del., a corporation of Delaware No Drawing. Application July 7, 1943,

Serial No. 493,755

23 Claims.

This invention relates to the electrodeposition of tin and is more particularly directed to tinplating compositions, tin-plating baths, and to processes for the electrodeposition of tin in the presence of a bath-soluble polyethercontaining a multiplicity of ether groups attached to aliphatic carbon atoms.

Tin-plating baths knownto the art are subject to disadvantages'which severely limit their usefulness. Organic addition agents have been employed in attempts to improve the character of deposit obtained from such baths and while the addition agents eflect some refinement of crystal structure and some modification in appearance the tin electrodeposits are of limited usefulness and the baths from which they are made are diflicult and uneconomical to employ.

Tin electrodeposits produced from prior art baths are usually crystalline at even rather low current densities and athigher current densities the deposits are spongy. They are not adherent and many are so poorly adherent that they can easily be removed from the base metal by rubbing.

Deposits thus produced with prior art baths are not readily amenable to brightening by heat fusion. These and \numerous other difficulties have hampered commercial development of tin electroplating processes.

It is an object of this invention to provide compositions, baths, and processes by the use of which there may be obtained tin deposits which are dense, adherent, and of good appearance. It is a further object to provide tin-plating baths. compositions, and processes by means of which there may be obtained deposits that can be readily brightened by fusion to a brilliant appearance and that can be subjected to lacquer baking operations without becoming discolored. Further objects of this invention will become apparent hereinafter.

The foregoing and other objects 01' this invention are attained by the use in a tin electrodepositing bath of a bath-soluble polyether containing a multiplicity of ether groups attached to aliphatic carbon atoms. By employing a bathsoluble polyether in tin electrodepositing baths one obtains deposits of a markedly improved ent invention in any tin-plating bath. For pur- 2 poses of illustration the following typical baths are given:

The following alkaline bath is of the type shown in the Oplinger Patent 1,841,978 and in the Wernlund et al. Patent 1,919,000.

\ Grams per liter Sodium stannate 120.0

Sodium hydroxide 7.5 Sodium acetate 15.0 Hydrogen peroxide 0.5

Bath V The following bath is not verystable when used over long periods of time but it is given because it is frequently mentioned in the literature and it is markedly benefited by the use of polyethers according to the present invention.

Grams per liter Stannous chloride 30 Sodium hydroxide";

Barri VI A bath of U. S. Patent 1,202,149 was made up as follows:

Grams per liter Stannous chloride, dissolved in 10% phosphoric acid 50 Bath VII Grams per liter Stannous chloride Hydrochloric acid (computed as H01) 25 Bath VIII Grams per liter stannous silicofluoride 110 liydrofluoric acid (computed as HF) 25 Bath IX A bath was mad ent 2,271,209 as lows:

4 Grams per liter stannous sulfate. 45 sulfuric acid (66 B.) 75

It will generally be found desirable to employ polyethers according to the present invention in acid baths of the prior art though as will be up as in the Schldtter Pat- "halogen-tin plating baths and the preferred baths are composed of an alkali fluoride-stannous chloride solution. These baths are described and claimed in Schweikher application, Serial No. 493,757, filed July 7, 1943, now Patent No. 2,407,579, September 10, 1946.

In using halogen-tin baths the ratio of fluoride to stannous chloride must be carefully selected and related to the operating pH of the bath as more specifically described below. The baths may be made up with stannous chloride and with an alkali fluoride, say sodium, potassium, or ammonium fluoride. When reference is made hereinafter to an alkali fluoride it will be understood that sodium, potassium, or ammonium fluoride or bifluorides may be used or mixtures of any of these may be employed.

The concentration of stannous chloride may vary from about thirty-seven and one-half to one hundred and fifty grams per liter and the alkali fluoride may similarly vary from thirty-seven and one-half to one hundred and fifty grams per liter. More specifically, it is desired to maintain the concentration of the stannous chloride and the alkali fluoride between about sixty and one hundred grams per liter.

More important, perhaps, than the mere concentration of stannous chloride and soluble fluoride is the molar ratio of these materials as related to the pH at which the bath is operated. An empirical formula which has been found satisfactoryis as follows:

fluoride and SnCl: is stanthan about grams per liter.

(2) The ratio of alkali fluoride to at chlo- 4 y ride for any given tin content is controlled by the value of It. It is then found that k is related to the pH of operation of the bath in such a way that for optimum operation at any given pH, In equals 0.55. However, it will be understood that in com-- mercial operation good results may be obtained with values of it between the broad limits of k=0.1 to k=l.0. It is more particularly preferred to stay within the limits, k=0.3 to k=0.7.

(3) The mol ratio of MF/SnClz should fall within the limits of 2 and 12. It is preferred that the ratio equal 6 when k equals 0.55.

(4) The pH of the formula is the maximum at which the bath is stable while the optimum pH for plating is within the range from about 1 to 5 and preferably the pH should be in the range from about 2 to 4. A bath formulation that is stable at a given pH may also be stable at a lower pH but the'preferred ranges are those within which addition agents are generally most effective.

In the practical application of the formula, since in ordinary use the pH of operation will be preselected, It will be fixed at the desired optimum value, and the amount of tin which it is necessary to have in the bath will be known, it may be best to express the equation in a form as shown below which may be used to calculate the amount of alkali fluoride compound required.

pH(mols snot MF The conditions selected are 0.33 mOl of stannous chloride to be used at a pH of 4. Then to calculate the mols of sodium fluoride using the above equation:

(0.33) 2.4 mols of sodium The acidity of the bath may be that which results from the bath constituents though adjustments of the pH may be made as desired. Generally, as mentioned above, the pH will fall within the range of about pH 1 to 5 while more specifically it is desired to have the pH from about 2 to 4.

In addition to observing the above conditions it will be found desirable so to adjust the bath composition as to lead to a static solution potential within'a predetermined range. The solution potential, P, should not fall outside the limits of the following two equations:

P=-0.055 pH -0.265 P=0.055 pH -0.370

In this formula, pH as indicated above, should have a value between 1 and 5 or, preferably, between 2 and 4.

After a solution has been prepared with constituents selected according to the methods given above in some detail, then the solution should be examined as to its potential. This can of course be done by making up a small amount of solution first rand then adjusting the entire bath composition in accordance with the findings. If the solution potential is below the values given for P in the above formulae, then it may be increased (made more negative) by increasing the MF/SnCl ratio; if the potential is too high it may be lowered by decreasing the MF/SnClz ratio. In adjusting the potential it will be noted that the potential increases with an increase in pH and decreases with a decrease in pH. Ordinarily potential will not be adjusted by changing the pH, though this means of adjustment is available if it is preferred to use some preselected ratio of MP to such.

The potential may be determined in any suitable manner as by connecting a potentiometer across a piece of tin metal and a ealomcl half cell in customary manner. The static solution potential of tin against the bath is then obtained as volts after corrections are made for the calomel half cell.

The bath temperature is that customarily used for tin-plating baths, and deposits are obtained at room temperature. It is ordinarily preferred, however, to use the bath at a temperature from about 55 to 65 C. in order to secure the optimum quality of deposit over a broad current density range.

Bath X Grams per liter Stannous chloride 75.0 Sodium fluoride 87.5 Sodium bifluoricle 3.7.5

Organic addition agents may advantageously be employed in any of the foregoing baths to improve the appearance, and characteristics of tin deposits. One or more organic addition agents may be used and there may be included in the bath, for instance, sulflte cellulose waste or a naphthol sulfonic acid. Gelatin or glue may be used to advantage for some uses but it will be found that glue and certain other organic agents are not too satisfactory when the deposit is to be heat-fused or lacquer-baked.

Metal brighteners may also be included in any of the foregoing baths and there may be used small amounts of a soluble compound of the triad metals of the iron group including iron, cobalt,

and nickel. There may, for instance, be used nickel chloride, nickel sulfate, or cobalt chloride, or cobalt sulfate, or iron chloride, or iron sulfate. The amount of the metal compound to use may readily be determined by a few simple tests and it will generally be found that from about 2 to 10 grams per liter is suitable. While iron exercises a beneficial effect on brightness, it promotes oxidation of stannous tin and is for this reason undesirable.

According to the present invention there is included in any tin electrodepositing bath, such as those shown above, a bath-soluble polyether containing a multiplicity of ether groups attached to aliphatic carbon atoms. The presence of such a polyether profoundly modifies the character of deposit obtained from such a bath.

The polyether may most conveniently be marketed in tin-plating compositions which contain some or all of the materials to be dissolved in water to make a tin-plating bath. Thus they may be sold in mixtures with tin compounds and any of the other bath components or additions as above described. Maintenance compositions may similarly be compounded with a polyether and other materials required for bath maintenance.

As has been indicated the polyethers should be bath-soluble. That is, they must be soluble enough to permit them to exercise an effect in the bath. They should be hydrophilic and even if they are very diflicultly soluble they may be added to a plating solution in a solvent or dispersed in other manners already well known to the art. Some of these polyethers behave very peculiarly in the bath in that they form stable suspensions which are effective. Apparently there is enough "bath-solubility for the agents to act. One very excellent agent, Igepal C," though it goes into solution very readily when simply added to the bath and is very effective therein, can nevertheless be separated from the bath by filtration.

\Vhile' any bath-soluble polyether may advantageously be employed for the modification of tin deposits according to the present invention it is preferred to use compounds containing a multiplicity of aliphatic ether groups. More specifically it is preferred to use compounds which contain a multiplicity of alkyleneoxy groups, -(CH2)n--O. the oxygen of which is attached to aliphatic carbon atoms.

The structure of a preferred group of compounds for use according to the invention may be represented as follows:

wherein R1 equals hydrogen, OH, or a monovalent organic radical, R4 equals hydrogen, OH, or a monovalent organic radical, and Y equals a polyether group.

More specifically R1 may be designated as hydrogen, OH, or a monovalent organic radical such as alkyl, alkoxy, aryl, aryloxy, aralkyl, alkaryl, acyl, amine, amido-, thioalkyl, and thioaryl. R4 may represent any of the groups just mentioned for R1. It may be the same as Rt or it may be different in a given compound. In the formulas given hereafter an eifort will be made to let the letters of the above and the following formulas represent the same substituent groups and throughout the application numerous examples will be given of groups which may be used in the above. formula or in any of the following. It is to be noted that in Formula 2 where R1 is followed by X and in other similar formulas R1 would obviously not have the value OH.

The preferred polyethers are of the class generally known. as polyalkylene oxides. The formulae for polyalkylene oxides may be shown thus:

2. RlX RzO MR4 wherein X equals oxygen or NH, R1 equals hydrogen or a monovalent organic radical, R2 equals a bivalent hydrocarbon radical, preferably -CH2 or CH2CH:, R4 equals hydrogen, OH, or a monovalent organic radical, and wherein n is a whole number at least as great as 2. Illustrative compounds and methods for their preparation are shown in United States Patent 1,970,578 to Conrad Schoeller and Max Wittwer. In the Schoeller ct a1 patent there are shown a large number of monovalent organic radicals which R1 and R4 in the above may represent.

In the United States Patent 1,970,578 Schoeller ct al. suggest deriving the organic radicals from caproic acid, lauric acid, oleic acid, ricinoleic acid, naphthenic acid, and many others. It is also suggested that instead of acids the monovalent organic radical may be derived by use of hexyl, octyl. decyl. undecyl, or doclec l alcohols, water-insoluble alkyl, cyclo-alkyl, aralkyl or aryl ethers of different polyhydric alcohols as for example crosylic, phenylic, benzyli-c, cyclohexylic,

-and na hthylic ethers of glycol or of glycerol.

Again the patent suggests that there may be used amines such as decylamine, undccyla'mine, cetylamine. and diphenylamine.

The disclosure of the Schoeller et a1. Patentpeat the entire disclosure of this patent here and it seems sufllcient simply to refer to the entire disclosure as representative of compositions suitable for the modification of tin electrodeposits according to the present invention.

Reference is similarly made to United States Patent 2,213,477, patented September 3, 1940, to Adolf Steindorff, Gerhard Balle, and Richard Michel. This patent also shows a large number of polyalkylene oxides which are suitable for the modification of tin electrodeposits according to the present invention. It will be seen that this patent shows a number of alkylene oxides substituted with an isocyclic hydrocarbon radical and with substituted isocyclic hydrocarbon radicals. As typical radicals there may be mentioned normal butylphenol, isobutyl-ortho-cresol, isobutylphenol, and the like. I

This patent particularly shows that alkylene oxides may be produced using such substituted lsocyclic compounds as ethylene oxide, propylene oxide, butylene oxide, butylene dioxide, cyclohexene oxide, glycide, epichlorhydrine, or the like.

It is further to be observed that many of the polyalkylene oxides produced according to the Steindorfi et al. Patent 2,213,477 are of unknown composition since they are prepared simply by reaction of alkylene oxides with complex materials,. the precise structure and compositionof which is not known. This is true, by the way, of the compositions preparedunder the Schoeller et al. Patent 1,970,578 but in every instance the structures given probably are an accurate representation of the formula and in any event the compounds may be called polyalkylene oxides.

As to the Steindorfi et al. Patent 2,213,477 it seems hardly necessary, to repeat here all of the details of methods of preparation or to give all of the specific compounds therein described since these are all suitable for use for the modification of tin deposits according to the present invention and it seems sufilcient for present purposes to make reference to this patent.

Another patent which shows polyalkylene oxides suitable for use for the modification of tin electrodeposits is the John Burchill, Henry Alfred Piggot and George Stuart James White Patent 2,144,647, patented January 24, 1939. This patent shows a large number of illustrative compounds and reference is made therein to British Patent 346,550, British 432,356, British 420,137, German 575,911, British 420,518, British 380,431, and British 434,424 as well as numerous other similar references. As to the Burchill et al. U. S. patent and the patents therein cited it seems suillcientforthe present purposes to point out that the compounds mentioned may be used according to the present invention and represent examples of illustrative polyalkylene oxides suitable for the'modification of tin deposits. Similarly there may be used the polyalkylene oxide polymers of U. S. Patents 1,921,378,

1,922,459, 1,976,678, 2,059,273, 2,134,429, 2,134,430, 2,167,073, 2,234,200, 2,275,378, and 2,275,379.

meric oxide in the presence of a catalyst, if necessary under pressure until a substantial proportion of polymeris formed (see Staudlnger, Die

Hochmolekularen Organischen Verbindungen,

1932, page 287, et seq.). The products, depending on their molecular weight, are solid, semisolid, or even fluid materials which are soluble in water. These products. are generally believed to be composed of a plurality 'of alkylene groups linked together in linear configuration through ether. linkageaand to bear hy-- droxyl groups at the ends of the polymericchain.

Thus, a polyethylene oxide is represented by HO-(CHzCHzO-MCHzCHaOH (Staudinger, 10c. cit.) These polymers are sometimes called polyethylene. glycols. It is understood that these products are not intended to'cover cyclic dimers of alkylene oxides such as dioxan.

Commercially prepared polyalkylene oxides of the type just described are satisfactory for use for the modification of tin electrodeposits according to the present invention.

While any bath-soluble polyalkylene oxide may be employed for the modification of tinplatiug deposits it is preferred to use polymers having a molecular weight over about 400. Poly-.

mers with molecular weights of 400, 600, 800,

a 1500, 4000, 5000, and 9000, for instance, have given excellent results.

For the calculation of the. molecular weights, the following formula may be used:

Molecular weight Hydroxyl number wherein hydroxyl numberhas its usual meaning, 1. e., the number of milligrams of potassium hydroxide necessary to neutralize the acetic acid obtained'by the saponification of the acetylated compound from one gram of sample. The methunder the trade name Carbowax" 1500.

The amount of a polyether to employ for the modification of a tin electrodeposit and tinplating bath will depend upon the specific bath and upon the conditions of use and can best be determined in each particular instance by a few simple trials. It may be indicated that in general about .001 to 25 grams per liter of a polyether will be found to exercise a desirable modiflcation of a tin-plating deposit. More specifically with respect to the unsubstituted polyethylene oxides it may be suggested that from about 0.001 to 5 grams per liter will be satisfactory while more specifically from about 0.01 to 2 grams per liter will be found satisfactory.

As examples of substituents for polyalkylene oxides the following may be tabulated:

1. Monohydric alcohols-Genera R-OH:

Methyl alcohol Cetyl alcohol Octadecyl alcohol -Phenyl ethyl alcohol Octadecenyl alcohol H n (F1) HOO-O-OH 1! HIGH! amass Probable reaction:

Examples of the procedure to be followed in preparing materials of this type are given in U. 8. Patent 1,922,459, Examples 1 and 2, and in U. 8. Patent 1,970,578, Example 19.

The reaction of an alcohol with ethylene oxide is typical of the reactions taking place between ethylene oxide and various other organic substituents. Ii the two probable reactions shown above are written out instead of using "n" to designate the repetitive ether groups, it will be seen that both of the above formulae are the same.

2. Polyhydric alcohols-Genera R(OH)=:

Ethylene glycol Sorbitol Pentaerythritol Probable reaction:

nlon n cnll n -o(cnlcn,o).n

Excellent examples are given in U. 8. Patent 1,922,459, Examples 1 and 2, 01' the procedure to be followed in preparing the condensation products of ethylene oxide with sorbitol and pentaerythritol.

3. Aldehydes-Genera R-CHO:

' Acetaldehyde Myristic aldehyde Benzaldehyde Phenyl acetaldehyde Probable reaction:

4. Acids-Genera R-COOH:

Acetic acid Stearic acid Benzoic acid Undecylenic acid Probable reaction:

no ofocfiA-on 5. Acids, polycarboxylicGenera R(COOH)=:

Oxaiic Maleic Phthalic Probable reaction:

coon nwnlcnlo ooo(onicn,o).n R\

coon monlcnlo coo(cmcn,o).n

8. Metals-Genera M4 V on:

Acetal Phenyl acetaidehyde dimethyl acetal Probable reaction:

OR unlcnlo ofonlomoxa' a-'-o 11-0 on on i o c o on a( mom alt-O 0 on on .a' oa' men,

Methods for the preparation 01' polyzlycol condensation products with acids and esters are given in U. 8. Patent 1,970,578, Examples 3, 1s,

and 22 respectively. The reaction with aldehydes probably proceeds by an esterification reaction between equal molecular quantities of the aldehyde and ethylene oxide as follows:

The excess ethylene oxide will then react in the same manner as with other esters.

The reaction between acetals and ethylene oxide may possibly proceed by one of the three methods shown, although this is purely a matter of conjecture, since no definite proof of a reaction of this type can be found in the literature. However, since a hemiacetal which contains an hydroxyl group will undoubtedly react in thersame manner as an alcohol, it can be assumed that the acetals will react in a similar fashion.

7. Phenols-Genera R-OH:

Phenol Catechol Naphthol Cresol Probable reaction: I I

R-OH 1| onion. n-o(cnlcnio).n

n40 olnl),on A phenol may be defined as an alcohol in which the hydroxyl group (or groups) is attached to an aromatic ring. They are therefore related to aliphatic alcohols, undergoing many of the same reactions and will react with ethylene oxide in an analogous manner.

amine with ethylene oxide is given in U. S. Patent 1,970,578, Example 13 and in 8. Patent 2,059,273. 9. Amides-Genera R'CONHa:

' Formamldcv Ben'zamide Stearic amide Probable reaction: v a A a-oozm Kenyan) oioiiilohm a-ooiooimyma Since'an amide is formed by the reaction of an organic acid with ammonia it may be considered as the amine ester of the organic acid and as such may be expected to follow the same general type of reaction as an ester.

enic or acetylenic linkage.

the fol- The invention is further illustrated b lowing examples:

Example 1 G./l. Stannous sulfate (SnSOr) 54 Sulfuric acid Carbowax 1500 .4 1.0

. 12 of the bath was the same as before the addition of Carbowax 1500.

Ezamplel Carbowax 1500 was used in a tin-plating composition made according to the formula of Bath IV:

' elf/1. Sodium stannate Malacca-311:0) "(120 Sodium hydroxide (NaOH) 7.5 Sodium acetate (Na-CaHaOz) 15.0 Hydrogen peroxide (H201) 0.5 Carbowax" 1500 2.0

Smooth, matte-white deposits of tin were obtained from this bath over the entire area of a test plate made in the Hull cell which indicates a current density range of from 5 to 140 amps/sq. ft. The physical appearance of the bath remained the same as before its adldition.

Example 5 Carbowax" 1500 was used in a tin-plating solution made according to the formula of Bath V:

, G./l. Stannous chloride (SnCl2-2H2O) Sodium hydroxide (NaOH) 75 Carbowax" 1500 4.0

The soft white waxy polyethylene oxide sold commercially under the trade name of Carbowax 1500 produced adherent sponge-free. deposits of tin that were ofa smooth matte-white texture over a plating range of from 5 to 100 noticeable physical change in the solution.

Example 2 A tin-plating bath according to the formula of Bath II was made as follows:

G./l. Stannous sulfate (SnSO4) 100 Sulfuric acid (computed as H2804) 30 Tartaric acid 30 Carbowax" 1500 2.0

The Carbowax" 1500 in this bath produced deposits that were similar to those obtained from the bath of Example 1, effectively stopping the tendency to form sponge or crystalline deposits and producing an adherent, smooth white deposit over a wide current density range. The physical appearance of the bath remained before its addition.

Example 3 A tin-plating composition according to the formula of Bath III was made up as follows:

- G./l. Stannous oxalate (SnCaOq) Ammonium oxalate (NH4)aC:O4-Ha0 60 Oxalic acid (H2C2O4) -15 Carbowax 1500 1.0

White, lustrous, adherent deposits entirely free from sponge were obtained from 5 to 40 amps/sq. ft. and smooth, matte-white deposits from 40 to 120 amps/sq. ft. by the presence of Carbowax" 1500 in the above bath. The physical appearance the same as amps/sq. ft. Its presence did not effect any "porous, non-adherent deposit of sponge tin.

A Hull cell test plate from this bath made before the addition of Carbowax 1500 proved to be by far the poorest deposit thus far obtained, the entire area of the plate being covered by a black, A test plate made after the addition of Carbowax" 1500 produced adherent deposits that were smooth and lustrous up to 40 amps/sq. ft.-, the deposition of sponge tin being almost entirely eliminated with the exception of a narrow Zone above 100 amps/sq. ft. The physical appearance of the bath was unchanged. v

Example 6 .Carbowax 1500 was used in a tin-plating composition made according to the formula of Bath VI:

Stannous chloride (SnCla-ZI-IzO) dissolved in 10% phosphoric acid 50 "Carbowax" 1500 5.0

The deposits obtained from this bath before adding Carbowax 1500 were very poorly adherent and did not cover well at current densities below 30 amps/sq. ft. The presence of Carbowax 1500 materially improved not only the adherence and covering power but produced spongefree deposits of a pleasing matte-white texture. The appearance of the bath was unchanged.

Example 7 Carbowax" 1500 was used in a tin-plating bath made according to the formula of Bath VII as follows:

-' G./l. Stannous chloride (SnC1a-2H2O) Hydrochloric acid (computed as 1101) 25 Carbowax 1500 5.0

The deposits obtained from this bath before adding Carbowax 1500 were simllarto those of the preceding bath. producing deposits that were i crystalline, poorly adherent, and scantily covered at current densities below 30 amps/sq. ft. The addition of Carbowax 1500 eliminated the growth of tin crystals and produced adherent, smooth, matte-white deposits above 15 amps/sq. ft, The appearance of the bath was unchanged.

Example 8 Carbowax" 1500 was used in a tin-plating hath made accordin8 to the formula of Bath VIII, as

follows: a

G./l. Stannous silicofluoride (SnSlFol 110 Hydrofluoric acid (computed as HF) 25 Carbowax 1500 2,0

The presence of "Carbowax 1500 produced deposits that were adherent, sponge-free and had a pleasing matte-white texture. Its presence did not alter the physical appearance of the bath. I

Example 9 Y Carbowax" 1500 was used in a tin-plating hath made according to the formula of Bath IX as follows:

Stannous sulfate (SnS04) 45 Sulfuric acid (66 B.) 75 Carbowax 1500 2.0

Example 10 Apreferrgd composition was prepared according to the formula described under Bath 1:. as

follows:

, 'Stannous chloride (SnClz'2H20) g./l 75 Sodium fluoride (NaF) --g./l.... 37.5 Sodium bifluoride (NaHF) g./l 37.5 Carbowa.x" 1500 -g./l.. 0.2 DH 2.5 Potential 0.472

Unlike the previous acid baths, the acidity of this bath was much less and could be controlled by means of its hydrogen ion concentration or pH. The effect of Carbowax 1500 was likewise more pronounced, requiring a much smaller concentration to produce optimum results and having a more beneficial action upon the character of deposits. Its presence produced deposits of tin that were smooth, lustrous and sponge-free over a current density range of from 3 to 120 amps/sq. ft. These deposits when heated, flowed to form a uniform, extremely bright surface. The physical apeparance of the bath was unaltered by the presence of'this material;

Example 11 The foregoing examples from 1 to 10 inclusive were repeated using "Carbowax 4000, a fairly hard, white, waxy substance in place of "Carbowax" 1500. The results were about the same, using the same amount of material as described in each of the above examples.

Example 12 4 i small amount of foam was produced during eiec trolysis when these materials were present.

Example 13 One gram per liter of Igepal C or CTA, in a solution prepared according to the formula of Bath -V produced adherent deposits that were semi-bright at current densities of from 3 to amp /sq. ft. and was also an effective anti-sponge agent. The presence of this material produced a small amount of foam during passage of the current.

Example 14 The presence of 0.2 g./l. of Igepal C or C'IA in a bath made according to formula IX produced adherent, smooth, lustrous deposits over a current density range of from 3 to 120 amps/sq. ft. The increased throwing power obtained by use of this material was remarkable, producing deposits in very deep recesses. Fusion of the tin deposit resulted in an exceptionally smooth and brilliant surface comparable to tin plate that has been "hot dipped. Foaming was produced during passage of the current when this material was present.

7 Example 15 The cream colored, pasty solid sold commercially under the name of Emulphorf 0 or 0N,

' was used to the extent of 0.1 to 5.0 g./l. in a solution prepared as described under Bath I. Best results were obtained with 0.8 g./l., the deposits having a lustrous semi-bright appearance from 3 to amps/sk. ft. and were easily "flowbrightened" by heating. This material is one of the most effective of the inventions as shown by this and other tests. A small amount of foaming was noted during electrolysis. I believe the product' is a polyethylene oxide manufactured under U. S. Patent 1,970,578

Example 16 Emulphor ON was also used in the remaining nine tin-plating baths as described previously and was found to produce excellent deposits when present to the extent of from 0.1 to 5.0 g./1. Particularly good results were obtained from Bath IV and Bath X, the deposits being uniformly lustrous and adherent over the entire area of 9. Hull cell test plate, which indicates a current density range of from 3 to 120 amps/sq. ft. or greater. The deposits obtained could be readily flowbrightened by heating to the proper temperature and they closely resembled hot dippedtinplate in appearance. A small amount of foaming was noted during electrolysis.

Example 17 Peregal O is a honey colored liquid that is believed to be a polyethylene oxide made in accordance with U. S. Patent 1,970,578. When added to a bath prepared as described under Bath I, the deposits were like those described under Example 15. The optimum quantity appeared to be 1.0 g./l., larger amounts than this affording no further improvement in the deposits. A small amount of foaming was noted during electrolysis of the solution.

Example 18 Peregal O was also used in Baths II to X inclusive and was found to be as effective as Emulphor ON, when present to the extentof 0.1 to 5.0 g./1., the amount required depending largely upon the type of tin bath used. As in Example 16, particularly excellent results were obtained when this material was used in Bath IV and Bath X, the deposits being uniformly lustrous and adherent without sin of sponging over the entire area of .a Hullcell test plate. The deposits were easily "flow-brightened by fusing at the proper temperature and closely resembled "hot dipped" tinplate in appearance. A small amount of foaming was noted during passag of the current.

Example 19 The brown gummy product obtained by reacting polyvinyl alcohol with ethylene, oxide was j readily soluble in water and was added in the form of its aqueous solution to the plating baths described under Baths I, IV, V, and X. Smooth, lustrous, uniform deposits, that were adherent and free from sponge were obtained from these' 1 baths by the presence of from 1.0 to 2.0 g./l. of the above product. A slight brown tinge and slight foaming were noted when this material was i present. I

Example 20 The white pasty semi-solid material obtained by reacting cetyl alcohol with ethylene oxide disduced considerable foam when added to the plating baths, but produced semi-bright deposits up to 40 amps/sq. ft. in Baths III and IX and semibrightdeposits up to 80 amps. per sq. ft. in Bath X, the remainder of the depositsxbeing'mattewhite in all cases.

Example 21 The product formed by reacting phenol with ethylene oxide was an amber colored liquid that readily dissolved in the plating baths or in water. This material was particularly effective in preventing the formation of sponge or crystalline deposits and was further effective in producing smooth, lustrous, adherent deposits from such baths as I, IV, IX, and X. It was particularly efiective in Bath X, the deposits obtained being semi-bright, lustrous and readily flow-brightened by proper heating.

Example 22 I A brown syrupy liquid was obtained by reacting 1 mol of beta-naphthol with mols of ethylene oxide to form a product in which n=5 in the This product produceda cloudy appearance and seemed to be somewhat insoluble when added to the baths described under baths III, IV, IX, and X. However, its eiIect was unimpaired by this apparent insolubility since the deposits obtained by the presence of from 0.2 to 2.0 g./l. were smooth, lustrous, adherent, and free from sponge, and could be readily flow-brightened to a brilliant mirror-like surface.

Example 23 and was in some respects better than Emulphoi ON described in Examples and 16 since it did not-produce foam.

Example 24 Four. diflerent products were obtained by reacting octadecyl alcohol with ethylene oxide in the ratio of 1:9.1, 1:11.6, 1:17, and 1:20 respectively to form materials that were cream to light brown semi-solids in appearance. Since their effect was much the same they will be described jointly rather than separately. One or more of each product obtained was used in all ten of'the plating baths described to produce deposits that were smooth and matte-white in Baths I, II, III,

. V, VI, VII, VIII, and IX, and deposits that were smooth and lustrous in Baths IV and X. All four materials caused considerable foaming during electrolysis, the lowest ratio material being somewhat less soluble than the others as indicated by a cloudy appearance when added to the plat- 26 solved quite readily in water and was added in the form of its aqueous solution to the baths dej scribed under III, IX and X. The material prcings of U. S. Patent 2,167,073 when present in such ing baths.

Example 25 The dark red liquid formed by reacting aniline and ethylene oxide was added to such baths as VIII, IX, and X in amounts of from 0.2 to 5 g./l. in which it dissolved to form clear and colorless solutions. as great as some of the better examples, but nevertheless was sufiicient to produce adherent matte-white deposits and greatly retarded the formation of sponge during electrolysis.

Example 26 The product obtained by reacting tannic acid and ethylene oxide in accordance with the teachbaths as I and X to the extent of from 0.1 to 10 g./l., produces smooth white adherent deposits rom Bath I Bath X.

Example 27 The colorless liquid obtained by reacting propylene oxide with octadecenyl' alcohol and which would probably conform to the formula:

cnuito cnomo ni was used in such baths as IV and X in amounts It was found to be somewhat insoluble since oily droplets were of from 0.1 to 3.0 grams per liter.

seen floating upon the surfaceof the baths upon its addition. However, sufflcient material was dissolved to be effective since the deposits obtained were smooth and lustrous over a wide area of a.

Hull cell test plate, the adherence and covering power being noticeably improved by its presence.

Example 28 Polyethylene glycol 400,

nofcn-cmowz is predominantly nonaethylene glycol in which 12:9, although small amounts of higher and lower glycols are also present. It is a water white liquid having an effect similar to the effect of Carbowax 1500 and 4000 when'used in sufficiently large quantities, which is approximately ten times the quantity of Carbowax 4000, so that to obtain best results it is necessary to add from 1 to 20 g./l. of this material, depending upon the characteristics of the individual plating baths.

Example 29 I The materials known as Tweens" are exam- Its effect upon the deposits was not 1 and smooth lustrous deposits from 17 pics of polyoxyalkylene derivatives of hexitol anhydride partial long chain fatty acid esters whose starting materials are the hexahydric alcohols, mannitol and sorbitol. They are usually amber colored liquids or solids easily soluble in water and having a profound effect upon the type of deposit obtained from the various tinplating baths. When present to the extent of from 0.1 to 5.0 g./l. in Baths I to X, inclusive, the deposits obtainable are modified to such an extent as to permit the deposition of smooth, white, adherent deposits. They are particularly beneficial in bath x from which smooth, lustrous, adherent, sponge-free deposits may be obtained by the presence of 0.4 gl. The Tweens used included those designated 20, 40, 60,-81, 80, 81, and 85.

I claim:

1. In a process for the electrodeposition of tin the step comprising effecting electrodeposition from an aqueous, tin-plating bath which contains a soluble tin compound, the process comprising eifecting electrodeposition in the presence of 0.001 to 25 grams per liter of a bath soluble polyalkyleneoxide of molecular weight over 400 as an addition agent.

2. In a process for the electrodeposition of tin the step. comprising 'eflecting electrodeposition from an aqueous. tin-plating bath which contains a soluble tin compound, the process comprising eflecting electrodeposition in the presence of 0.001 to 25 grams per liter of a bath-soluble polyalkylene oxide terminally substituted with a monovalent organic radical and having a molecular weight over 400 as an addition agent.

3. In a process for the electrodeposition of tin the step comprising efiecting electrodeposition from an aqueous, tin-plating bath which contains a soluble tin compound, the process comprising effecting electrodeposition in the prestains a soluble tin compound, the process comprising eflecting electrodeposition in the presence of 0.001 to 25 grams per liter of a bath-soluble polyethylene oxide terminally substituted with a substituted isocyclic radical and having a molecular weight over 400 as an addition agent.

ence of 0.001 to 25 grams per liter of a bath-soluble polyalkylene oxide terminally substituted with a monovalent aliphatic radical and having a molecular weight over 400 as an addition agent.

4. In a process for the electrodeposition of tin the step comprising effecting electrodepositionfrom an aqueous, tin-plating bath which contains a soluble tin compound, the process comprising efiecting electrodeposition in the presence of 0.001 to 25 grams per liter of a bath-solu- 8. In a process for the electrodeposition of tin the step comprising efiecting electrodeposition from an aqueous bath which contains analkali fluoride, stannous chloride, and 0.001 to 25 grams per liter of a bath-soluble polyalkylene oxide 01' a molecular weight over 400 as an addition agent,

the composition having a stannous chloride concentration of between about 37.5 and 150 grams per liter. and the bath satisfying the equation:

k (mois MF) mols SnCl,

wherein the following conditions are simultaneously true; pH is equal to about 1 to 5, It has a ,the static solution of tin in the bath being equal in volts to from o.055 pH -0.2c5 to -o.055 pH 0.37o.

mols SnCl, V

wherein the following conditions are simultaneously true; pH is equal to about 1 to 5, is has a value from 0.1 to 1.0, MP is alkali fluoride, and

ble polyalkylene oxide terminally substituted with a substituted isocyclic radical and having a molecular weight over 400 as an addition agent.

5. In a process for the electrodeposition of tin the step comprising effecting electrodeposition from an aqueous, tin-plating bath which contains a soluble tin compound; the process comprising effecting electrodeposition in the presence of 0.001 to 25 grams per liter of a bath soluble polyethylene oxide terminally substituted with a monovalent organic radical and having a molecular weight over 400 as an addition agent.

6. In a process for the electrodeposition of tin the step comprising effecting electrodeposition from an aqueous, tin-plating bath which contains a soluble tin compound, the process comprising effecting electrodeposition in the pres-.

from an aqueous, tin-plating bath which conthe mol ratio MF/SnClz is about from 2 to 12, the static solution potential of tin in the bath being equal in volts to from '-0.055 pH 0.265to k( mols MF) mols sncl,

wherein the following conditions are simultaneously true; the pH is equal to about 1 to 5, It has a value from 0.1 to 1.0, MB is alkali fluoride, and the mol ratio MF/SnClz is about from 2 to 12, the static solution. potential of tin in the bath being equal in volts to from -0.055 pH -0.265 to -0.055 pH -0.370.

11. A tin electrodepositing composition comprising an alakali fluoride, stannous chloride, and 0.001 to 25 grams per liter of a bath-soluble polyethylene oxide terminally substituted with a monovalent organic radical and having a molecular weight over 400 as an addition agent, the composition upon being dissolved in water being adapted to give a stannous chloride concentration of between about 37.5 and 150 grams per liter and satisfying the equation:

k(mols MF) pH mols SnCl,

wherein the following conditions are simultaneously true; the pH is equal to about 1 to 5, It has a value from 0.1 to 1.0, MP is alkali fluoride, and the mol ratio .MF/SnCh is about from 2 to 12, the static solution potential of tin in the bath being equal in volts to from 0.055 pH 0.265 to 12. An aqueous, tin electrodepositing bath containing 'a soluble tin compound and 0.001 to 25 grams per liter of a bath-soluble polyalkylene oxide of a molecular weight over 400 as an addition agent.

13. An aqueous, tin electnodepositing bath containing a solubletin compound and 0.001 to 25 grams per liter of a bath-soluble polyethylene oxide terminally substituted with a monovalent organic radical and having a molecular weight over 400 as an addition agent.

14. A tin electrodepositing bath comprising an aqueous solution of an alkali fluoride, stannous chloride, and 0.001 to 25 grams per liter of a bathsoluble polyalkylene oxide of a molecular weight over 400 as an addition agent, the stannous chloride concentration being between about 37.5 and 150 grams per liter and the bath satisfying the equation:

k(mols MF) mols SnCl wherein the following conditions are simultaneously true; the pH is equal to about 1 to 5, k has a valuefrom 0.1 to 1.0. MF is alkali fluoride, and

the mol ratio MF/SnClz is about from 2 to 12, the static solution potential of tin in the bath being equal in volts to from 0.055 pH 0.265 to 0.055 pH 0.370.

15.'In a process for the electrodeposition of tin the step comprising effecting electrodeposition from an aqueous, tin-plating bath which contains a soluble tin compound, the process comprising .eifecting electrodeposition in the presence of 0.001 to 25 grams per liter of a bathsoluble, unsubstituted polyethylene oxide having amolecular weight over 400 as an addition agent.

16. In a process for the electrodeposition of tin the step comprising effecting electrodeposition from an aqueous bath which contains an alkali fluoride, stannous chloride, and 0.001to 25, grams per liter of a bath-soluble, unsubstituted polyethylene oxide having a molecular weight over 400 as an addition agent, the composition having a stannous chloride concentration of between about 37.5 and 150 grams per liter and the bath satisfying the equation:

k(mo1s MF) mols SnChwherein the following conditions are simultaneously true: pH is equal to about 1 to 5, R: has a value from 0.1 to 1.0, MF is alkali fluoride, and the mol ratio MF/SnClz is about from 2 to 12,

- the static solution potential of tin in the bath being equal in volts to from 0.055 pH 0.265

polyethylene oxide having a molecular weight over 400 as an addition agent, the composition having astannous chloride concentration of between about 37.5 and grams per liter and the bath satisfying the equation:

k(mois MF) mols SnCl,

polyethylene oxide having a molecular weight over 400 as an addition agent. a

19. A tin electrodepositing bath comprising an aqueous solution of an alkali fluoride, stannous chloride,. and 0.001 to 25 grams per liter of a bath-soluble, unsubstituted polyethylene oxide of a molecular weight over 400 as an addition agent, the stannous chloride concentration being between about 37.5 and 150 grams per liter and the bath satisfying the equation: I

pH k(mols MF) mols SnCl,

wherein the following conditions are simultaneously true: the pH is equal to about 1 to 5, It has a value from 0.1 to 1.0, MF is alkali fluoride, and the mol ratio MF/SnClz is about from 2 to 12, the static solution potential of tin in the bath being equal in volts to from 0.055 pH 0.265 to 0.055 pH -0.370. 20. In a process for the electrodeposition of tin the step comprising effecting electrodeposition from an aqueous, tin-plating bath which contains a soluble tin compound, the process comprising effecting electrodeposition in the presence of 0.001 to 25 grams per liter of a bathsoluble, unsubstituted polyethylene oxide having a molecular weight between 1500 and 9000 as an addition agent. I

21. In a process for the electrodeposition of tin the step comprising eflecting electrodeposition from an aqueous bath which contains an alkali fluoride, stannous chloride, and 0.001 to 25 grams per liter of a bath-soluble, unsubstituted polyethylene oxide having a molecular weight between 1500 and 9000 as an addition agent, the composition having a stannous chloride concentration of, between about 37.5 and 150 grams per liter and the bath satisfying the equation:

k(mols MF) mols SnCl wherein the following conditions are simultaneously true: pH is equal to about 1 to 5, It has a value from 0.1 to 1.0, MI is alkali fluoride, and the mol ratio MF/SnClz is about from 2 to 12, the static solution potential of tin in the bath beingequal in volts to from 0.055 pH 0.265 to 0.055 pH -0.370.

22. An aqueous, tin electrodepositing bath containing va soluble tin compound and 0.001 to 25 grams per liter of a bath-soluble, unsubstituted polyethylene oxide having a molecular w eight between 1500 and 9000 as an addition agent.

23. A tin electrodepositing bath comprising an aqueous solution of an alkali fluoride, stannous chloride, and 0.001 to 25 grams per liter of a bath-soluble, unsubstituted polyethylene oxide of 21 a molecular weight between 1500 and 9000 as an addition agent, the stannous chloride concentration being between about 37.5 and 150 grams per liter and the bath satisfying the equation:

k(mols MF) PH- mols SnCl,

wherein the following conditions are simultaneously true; the pH is equal to about 1 to 5, is has a value from 0.1 to 1.0, MP is alkali fluoride, and the mol ratio MF/SnClz is about from 2 to 12, the static solution potential of tin in the bath being equal in volts to from 0.055 pH 0.265 to 0.055 pH 0.370.

RAYMIOND A. HOFFMAN.

REFERENCES CITED The following references are of reoord in the file of this patent:

15 Number UNITED STATES PATENTS Name Date Brown Oct. 25, 1938 Barrett et a1. Aug. 13, 19,40 Steindorfi et a1. Sept. 3, 1940 Nachtman Dec. 16, 1941 Schlotter Jan. 27, 1942 Johnson Mar. 3, 1942 Loder et a1. Jan. 9, 1945 Nachtman Mar. 6, 1945 Beaver Dec. 18, 1945 Schweikher Sept. 10, 1946 FOREIGN PATENTS Country Date Great Britain Apr. 16, 1931 Great Britain July 22, 1935 Great Britain Feb. 27, 1936 OTHER REFERENCES Industrial and Engineering Chemistry, Jan. 1941, pages 16-22. 

